1. Technical Field of the Invention
The invention relates to expandable and collapsible shielding materials having parallel hollow cells running perpendicular to the direction of expansion and collapse which are often used as movable window blinds, and in particular to a continuous band method for producing such a material. Furthermore, the invention includes an apparatus for practicing the method.
2. Description of Related Art
Such shielding materials are now well known as a means of providing a movable insulating blind for windows. Examples of such material are shown in U.S. Pat. Nos. Re. 30,254 to Rasmussen, 4,388,354 to Suominen, and 4,603,072 to Colson. While the products are known, the existing methods of producing these types of shielding materials economically and in large quantities are generally less than satisfactory.
U.S. Pat. Nos. 4,288,485 to Suominen and Re. 31,129 to Rasmussen both disclose methods for producing expandable and collapsible type insulating material. Both of these methods consist basically of applying adhesive to one side of a flat, tubular strip and then winding it onto a receiving wheel or wheels to produce a loop of tubular layers which are bonded together one on top of another.
One significant problem with this method of manufacture is that the adhesive between the layers dries while the loop is being wound up in a curved state. Therefore, the resulting stack of tubular layers has a curved set, even after it is cut and pulled into a straight section. This curved set in the final product causes the resulting product to have an unattractive appearance due to warpage. The warpage is often not initially present, but shows up some time later due to the fabric memory.
U.S. Pat. Nos. 4,450,027 and 4,631,108 to Colson show an alternative method and apparatus for making a similar product. But while this method has overcome the problem of the curved set, it has done so by winding the fabric onto a flat rack which requires very complicated machinery and speed control due to the constantly changing velocity of the fabric as it is wound onto the rack.
It is therefore an object of this invention to provide a method and apparatus for producing a continuous band expandable and collapsible shielding material which does not have a curved set and therefore is free from discontinuities, warps and uneven lines associated with such a curved set.